Many various types of prior art data storage apparatus and methods are known. Of the known data storage systems, two of the more widely used types are those which comprise tape drives and those which employ hard disk drives. As the respective names imply, tape drives and hard disk drives each employ specific types of media on which to store data. That is, tape drives employ r eels of magnetic tape strips as data storage media, while hard disk drives employ one or more stacked hard disk “platters” as data storage media.
Typically, the magnetic tape type of media is supported on one or more reels which are enclosed in a cartridge shell, or casing. The tape, together with the cartridge shell, is referred to as a “tape cartridge.” Such tape cartridges are configured to be selectively placed into a slot, or opening, of a tape drive, wherein the tape is extracted from the cartridge so that data can be read from, and/or written to, the tape. When the reading, and/or writing, of the tape is completed, the tape is wound back into the cartridge, and the tape cartridge is removed from the slot of the tape drive and placed on a storage rack or the like. The cartridge configuration of the tape facilitates ease of handling a great number of tapes, wherein each tape cartridge can be quickly exchanged between a storage position and a tape drive for read/write operations.
Tape cartridges typically adhere to one of a plurality of accepted cartridge form factors. By “cartridge form factor” I mean a given set of standardized physical configurational and dimensional criteria which apply to the design of cartridges. Various specific data storage cartridge form factors have been developed, and include cartridge form factors known by the designations of: DAT (Digital Audio Tape); DDS (Digital Data Storage); DLT (Digital Linear Tape); and LTO (Linear Tape Open) The adherence of tape cartridges to a given known standard cartridge form factor allows for wide spread interchangeability of tape cartridges which adhere to a common form factor.
Often, a plurality of tape cartridges are employed in conjunction with an automated library system or the like. Automated library systems typically comprise storage racks or supports, at least one robotic cartridge handling device, and at least one tape drive. The storage racks are configured to support the plurality of tape cartridges. The robotic cartridge handling device is configured to selectively move given tape cartridges from the storage rack to the tape drive, and to insert the tape cartridge into the slot of the tape drive. While the tape cartridge is in the slot of the tape drive, read/write operations can be performed on the tape. The robotic cartridge handling device is also configured to remove the respective tape cartridges from the tape drive after the read/write operations have been performed on the tape cartridge, and to replace the tape cartridges onto the storage rack.
Thus, a typical automated library system is configured to move tape cartridges between respective stored positions on a storage rack and a tape drive, as required. Generally, a controller or the like is used to control the operation of the automated library system. For example, a controller, when connected in signal communication with the robotic handling device, can be configured to direct the robotic handling device to move a specific, given tape cartridge from its stored position on the storage rack to a tape drive in response to a requirement to retrieve given data which is stored on the given tape cartridge. As is evident, tape cartridges, when used in conjunction with an automatic library system, for example, are relatively well-suited for long-term storage and archiving of large amounts of data. However, one disadvantage of magnetic tape is that data reading/writing operations are relatively slow compared to magnetic hard disks, for example. Moreover, accessing random portions of data from magnetic tape can be significantly slow compared to magnetic hard disks.
Hard disks are generally known to provide exceptionally rapid data storage and retrieval, as well as high levels of storage capacity. Hard disks are typically employed in “disk arrays.” A typical disk array comprises a frame or rack that is configured to support a plurality of modules or the like which each contain one or more hard disks along with a disk drive. The modules which contain the hard disks and disk drive are generally configured to be semi-permanently supported on the frame or rack. That is, the modules are generally configured to remain supported in place on the frame or rack and communicatively linked with at least one other device, except for repair and/or replacement of a malfunctioning module in which case the malfunctioning module is communicatively disconnected from the other respective devices and removed from the array. In other words, prior art data storage methods and apparatus which employ a plurality of hard disks are typically limited in regard to the functional use of each hard disk to situations in which all of the hard disks are communicatively linked together so as to be immediately available, on demand, for read/write operations. As a result, the prior art use hard disks for data storage necessitates relatively large and cumbersome disk arrays which comprise a great number of modules.
What are needed then, are data storage methods and apparatus which achieve the benefits to be derived from similar prior art devices, but which avoid the shortcomings and detriments individually associated therewith.